Apparatus for the continuous purification of suspensions or sludges, especially of fibrous pulp of the paper industry



.Aug. 22, 1944. H. BANNING 2,356,497

APPARATUS FOR THE CONTINUOUS PURIFICATION OF SUSPENSION-S OR SLUDGES,ESPECIALLY OF FIBROUS PULP OF THE PAPER INDUSTRY Filed Aug.- 29, 1939 2Sheets-Shet 1 flgfl 10 3 7% hie/Mar HELMU 7' H BflN/V/NG Aug. 22, 1944.H. BANNING 2,356,497

APPARATUS FOR THE CONTINUOUS PURIFICATION OF SUSPENSIONS OR SLUDGES,ESPECIALLY OF FIBROUS PULP OF THE PAPER INDUSTRY Filed Aug. 29, 1959 2Sheets-Sheet 2 Fig.4 1

w Ham/7W a/z/v/w/va PatentedA'ug. 22, 1944 APPARATUS FOR THE CONTINUOUSPURIFI- I CATION F SUSPENSIONS 0R SLUDGES, ESPECIALLY OF FIBROUS PULP OFTHE 7 PAPER INDUSTRY Helmuth Banning, Duren, Germany; vested in. theAlien Property Custodian Application August 29, 1939, Serial No. 292,38

- In Germany August 31, 1938 Claims. (Cl. 210-68) This invention relatesto a method of, and apparatus for, the continuous purification ofsuspensions or sludges, especially of, fibrous pulps of the paperindustry, by means of a'centrifugal apparatus having a fixed outer wallguiding the pulp. The invention aims at a centrifugal method which isnot interrupted by a periodical emptying out of the heavy particlesaccumulated in the centrifugal spaces. p

In the case of the known types of centrifugal apparatus a compacted firmcushion of fibres is formed at the closed wall of the rotary centrifugaldrum, and the heavy contaminations accumulate in and on that cushion.This is disadvantageous in that the centrifugal drum becomes after acertain period of operation, filled with these retained particles ofdirt, whereupon the apparatus has to be stopped for cleaning purposes.

Centrifugal machines are also known which act as centrifugal sortingmachines, the suspension of pulp being forced through a rapidly rotatingperforated drum. In the case of these sorting machines, thecontaminations are only sorted out according to the widths of theperforations of the perforated drum. Contamlnations are retained infront of the sieve (considered in the direction of the current) whilethe fine fibres pass through it. The disadvantage of these knownmachines is due to the fact that the sieves are .very liable to clogginCentrifugal machines also acting as centrifugal sorting machines arealso known, where the pulp and the contaminations of greater specificgravity pass through a rapidly rotating drum sieve to a chamber outsidethe drum. In such cases, the

I contaminations are mainly separated out by gravity in a casing whichis conically widened in the direction towards the outlet. Thus, theouter chamber of the centrifugal machine contains the contaminations aswell as the pulp to be purified,

the two being not spacially separated. The drum sieve only serves thepurpose of retaining contaminations of greater dimensions. As thecontaminations and the pulp to be purified are present sideby side, itcannot be avoided that contaminations getinto the outlet for the pulp tobe purified.

In order to avoid these disadvantages, it is,

according to the invention, proposed to produce apertures in the drum tothe outside.

passed through the interior of the drum in axial direction, and thecontaminations of greater specific gravity'are allowed to pass throughthe In this connection it is convenient to keep in an axial movemeht thesuspension which has passed to heavy con- .therefroni are, to a largeextent, separated from each other in the process according to theinvention, and in contradistinction to the known processes, aparticularly effective separation of the pulp to be purified and of thecontaminations is obtained in a continuous operation. The purified pulpmay be passed on for further use without being subjectedto any furtherpurifying opera-' tion. When purifying a suspension ofpaper pulp, thepurified pulp may, for example, be passed on direct to the papermachine.

In the apparatus for carrying out the process according to theinvention, the sludge or'pulp suspension to be purified is introducednear the shaft into a fixed centrifugal casing which is closed on allsides. A drum perforated'in some places rotates with high speed insidethe centrifugal casing, imparts rotation to the pulp and divides thecentrifugal space into two separate centrifugal zones. The suspensiontobe purified enters the inner centrifugal zone through an aperture inthe end wall of the casing and leaves it, purified, at the other end.The contaminations pass through the apertures in the centrifugal drumand collect in a suspension of pulp at the wall of the outer casing,which suspension is also subjected to the centrifugal effect and becomesmore and more dense towards the outer side. The contaminations aredirectly withdrawn from the outer centrifugal zone either'continuouslyor periodically.

Sedimentation along the drum in the inner centrifugal zone may, in thecase of the apparatus according to the invention, be repeatedlyinterrupted by substantially'radial surfaces which deflect the currentof pulp either towards the I inside or towards the outside, therebyfacilitating the separation of the contaminations. The contaminationsare.retained by the surfaces, in

front of which the passage apertures in the drum are preferablyarranged. The contaminations pass through these apertures into the outerzone. Sedimentation in the outer zone may also be effected in separatesteps, the heavy substances being collected at the wall of thecentrifugal body, perhaps by ribs or shoulders, from where they are ledoff separately. l

' The whole length of the two centrifugal zones -is fully utilized forpurifying, the pulp in the inner zone being quickly accelerated totherotational speed of the drum by means such as a pump, and, afterpurification, being removed from the centrifugal machine at once. As afurther modification of the centrifugal machine,.

the outer wall thereof may, for example, be given a special conicalshape so as to increase the percentage of contaminations in the pulp atthe point of withdrawal. Similarly, a definite control of thecentrifuging and of the sedimenting operations and of the withdrawal ofthe contaminations may be effected by p oviding inside the centrifugalspace a circuit from the inner to the outer zone and back to the inletside.

In the drawings, a number of embodiments of apparatus according to theinvention are diagrammatically shown by way of example.

Fig. 1 is a vertical, longitudinal section of a centrifugal machine,

Figs. 2 and 3 are side views of centrifugal machines having modifiedcasings.

Figs. 4 and 5 are vertical,longitudinal sections of centrifugal machineswith different means for guiding the pulp,

. Fig.6 is a vertical, longitudinal section of a. different embodimentof a centrifugal machine, Fig. '7 is a cross-section of a centrifugaldrum,

and l Fig. 8 is a view of an end face of a centrifugal drum.

The centrifugal machine consists, for example, of a cylindrical casingl, at one end face 2 of which the suspension is admitted through acurved tube fitting 3. The suspension leaves through the curved tubefitting 5 at the opposite end wall 4. The centrifugal shaft 6 issituated inside the casing, has its bearings outside there- I of, and israpidly rotated by means of a suitable drive. Inside the fixedcentrifugal casing, the

shaft carries the frusto-conical body 1. Radial arms 8, mounted on thebody 1, carrythe perforated centrifugal drum 9. For the purpose ofaccelerating the pulp admitted through the tube fitting 3, the arms atthe front end of the body I may be shaped to form vanes 10.

Fitted to the outer wall of the casing is a tube l i for the withdrawalof the suspension accumulated'inside the wall, which suspension containsthe particles of dirt. Withdrawal can either be effected continuously insmall quantities, or the aperture is opened periodically as soon asconsiderable quantities of dirt have accumulated inside the outer wall.a

The body 1 forces the admitted pulp, which moves along the shaft, toflow radially, whereby it enters the zone of influence of the rotatingcentrifugal drum 9 and is also rotated. The current of pulp followingbody I forces said pulp along the drum having a perforated wall, so thatthe pulp fills the entire internal space-of the closed casing l of'thecentrifugal machine. While the pulp passes through the centrifugal zonealong thecylindrical wall of the drum which may, for example-, beperforated, an increase in the density of the suspension occurs in thedirection towards the outer wall of the casing, but this increase islimited because of the setting up in the space between drum and casingof eddy currents near the fixed wall prevents further densification. Theheavy contaminations contained in the current of pulp are caused to passthrough the apertures in the wall of the drum and collect in thesuspension contained between the fixed wall and the rotating wall of thedrum. The purified pulp on the other hand, flow's along the inner wallof the perforated drum to the other end of the closed casing and leavesthrough an opening 9-5 in the end wall 9--a.

It is advantageous to accelerate the admitted pulp initially, by aradial system of vanes H), to

the circumferential speed of the rotating perforated drum, or nearly tothat speed. This imparts to the pulp the required circumferential speedalready at the front end of the rotating drum, so that the whole lengthof the latter may 'be utilized for the separation of the heavyparticles. The fixed casing may be so constructed that the dirtseparated out collects mostly in the vicinity of the connecting fittingsof the pipe ll. According to Fig. 2, the outer shell of the casing 3| isconstructed conically, and the tube H is connected at a point where thediameter of the cone is the greatest, and where the particles of dirtmainly collect. The perforated drum 39 may also be constructedconically.

As shown in Fig. 3, it is advantageous to have the outer wall of thecasing widening in the direction towards the inlet and not in thedirection towards the outlet, in order to keep the collecting point ofthe dirt as far as possible from the outlet 5 for the purified pulp.

Fig. 3 shows a centrifugal machine of this type having an outer shell 32set oil in steps. Tubes I I are connected to each end of a step. Insteadof a cylindrical outer shell, an outer shell having conical steps of anyother type may also be employed (Fig. 5). A further improvement in thepurifying process is obtained by arranging annular shoulders I2 insidethe rotating drum 38, or of rings I 4 inside the fixed outer shell I, asis shown in Fig. 4. There, the body 31 carries rings l3, and therotating drum 38 carries annular shoulders l2 projecting towards theinside, the pulp being alternatingly deflected to the inside and to theoutside 'by the .edges of these parts. The pulp flowing along is dammedup or obstructed by these shoulders I2 and rings I3, whereby a slowerfiow'of the pulp is caused in these places and also eddying currents atthe edges of the shoulders I2 and the rings l3. This favours adeposition of the-dirt in front of the shoulders l2 and the passingthereof through the holes in the drum.

The shoulders I! are conveniently arranged to widen conically in thedirectionof the axial flow, so that heavy particles may depositbehindthe shoulders, being separated out of the pulp passing over theedges of the shoulders.

It is also advantageous to sub-divide the outer centrifugal zone byannular rings I, in order to prevent a movement of the dirt along theouter wall towards the outlet of the purified pulp. The largest dirtparticleswill deposit in the first section of the outer centrifugalzone, and comparatively small proportions of dirt will be washed throughthe pipes II of the sections gradually nearing the outlet. The provisionof the shoulders I2 and rings l4 results in that the dirt is thrown backinto the preceding'zone in which it was separated out, so that dirt,once it has been separated out, can no longer reach the outlet end ofthe centrifugal machine.

According to Fig. the portions of the fixed casing 33 form conicalsub-divisions. In order to obtain the advantages described above, thecones forming the casing widen in the direction towards the outlet forthe purified pulp and are connected with the adjoining conicalportion byradially disposed surfaces. The tubes It are attached at the bottom ofthe centrifugal machine in front of the respective 'radial surfaces.Radial ribs [5 are conveniently provided on the outer shell of thecentrifugal drum-3E, deflecting towards the outer wall the heavyparticles separated out in the outer zone.

According to Fig. 5, the inlet side of the drum 35 is constructed as arotor 34 of a pump. A different system of guiding the pulp in the innerzone of the centrifugal drum 36 is-obtained by an alte'rnatingarrangement of radial partition walls I6 between the drum 36 and thebody 35. Openings I! are provided in the partition walls and arealternatingly disposed near the drum and-near the body, or half waybetween the two, whereby passages for the pulp are formed at differentdistances from the axis of rotation. This results in that even thefinest contaminations are separated out, the specific gravity of whichapproximates that of the pulp fibres.

Fig. 6 shows a construction of the casing 33 having a helical inlet F8for the pulp and a helical outlet l9 for the pulp. This permits autilisation of the kinetic energy of the pulp as admitted, in.

order to impart a rotary movement to the admitted pulp, whereby a savingin energy is obtained. Constructing the outlet portion spirally permitsachieving a higher outlet pressure. In the case of this embodiment, thecasing 33 is, for example, conically widened in the direction towardstneinlet, slightly first and more later, whereby an annular pocket 20 isformed from which the dirty pulp is withdrawn. A conical tube 2!surrounding the shaft is provided for'the retention of the lightconstituents. That tube receives the light contaminations which, in viewof the centrifugal force, move towards the shaft, so that they may bewithdrawn throughthe pipe 22.

The construction of the rotary perforated drum 29 may also vary,depending on the type of suspension to be purified. For the separationof finer contaminations it is sufficient to use a shell perfo rated byfine holes, while larger perforations are provided forthe purificationof pulp having coarser contaminations.

A convenient embodimentof a centrifugal drum is shown in Fig. 7. Rings24 serving for the retention of the contaminations of the suspensioncarry ribs 25 which extend axially and leave between each other slotsthrough which the heavy particles pass.

An undesirable passage of pulp from the outer to the inner centrifugalzone, particularly at the outlet end of the-rotating drum 29 isprevented by providing the rotating drum 29 at its ends with annularrings 26 which are closely adjacent to inwardly extended flanges 33a ofthe casing 33.

Channels ,2! (Fig. 8) are provided in the outer surfaces of the annularrings 26, or corresponding ribs are attached thereto, their directionbeing approximately radial. By means of a suitable width of these rings,it is possible to produce a suitable current between the flanges 33-a ofthe casing 33 and the rotating annular rings 26, which tinuouslywithdrawn from the outer part of the casing and supplied back to theinlet. In this connection it is'convenient to withdraw that quantity ofpulp not at the outer circumference of the casing, where the greatestproportcn of dirt collects, but at a point somewhat nearer to the axis.What I claim as new and desire to secure by Letters Patent is:

1. An apparatus for the continuous purifica tion of suspensions orsludges particularly of fibrous pulp as used in the paper industry,which contain contaminations'of higher specific gravity, comprising afixed casing, an enclosed drum having inlet and discharge openings atits ends, respectively, and aperture only on its cylindrical face,rotatably arranged in said casing, said drum being provided withinwardly and outwardly extending radial annular members formingcommunicating annular compartments adjacent the cylindrical wall of saiddrum, said apertures being of a size exceeding that of thecontaminations, inlet means for unobstructedly admitting the suspensionand the contaminations into the interior of the drum. outlet means fordischargingthe purified suspension from the interior of the drum at theend of the drum, said outlet being restricted to cause a higher densityof pulp in the space between said drum and casing and an accumulation ofsaid contaminations in said space, an additional outlet for purifiedsuspensions concentric with said drum and of such dia-meter that saidsuspensions flow freely therethrough in a substantially axial direction,and means for the rapid rotation of the drum to cause contaminations ofhigher specific gravity to pass out through said apertures.

2. Apparatus according to claim 1, where the widths of the inlet meansare smaller than those of the outlet means.

3. Apparatus according to claim 1, having the outlet opening disposedcentrally, relatively to the axis of the drum, in the casing, and havinan outlet opening of a diameter which is smaller than that of the drum.4. Apparatus according to claim 1, where the ends of the drum haveinwardly projecting rims. 5. Apparatus for the continuous purificationof suspensions or sludges, especially of the fibrous pulp as used in thepaper industry, which contain contaminations of higher specific gravity,comprising a fi;-.ed casing, an enclosed drum having inlet and dischargeopenings at its ends, respectively, and apertures only on itscylindrical face, rotatably arranged in the casing, said drum beingprovided with inwardly and outwardly extending radial annular membersforming communicating annular compartments adjacent the cylindrical wallof said drum, said apertures being of asize exceeding that of thecontaminations, inlet means for admitting the suspension and thecontaminations into the interior of the drum, outlet means forunobstructe dly discharging the purified suspension from the interior ofthe drum at one end of the drum, said outlet being restricted to cause ahigher density of pulp in the ,space between said drum and casing and anaccumula-' tion of said contaminations in said space, an additionaloutlet for purified suspensions concentric with said drum and of suchdiameter that said suspensions flow freely therethrough in asubstantially axial direction, means for the rapid rotation of the drumto cause contaminations of higher specific gravity to pass out throughmid apertures, means arranged on the driving shaft inside the drum andadapted to guide the admitted suspension radially towards the wall ofthe drum and then axially to the end of the drum, and means foraccelerating the "radially moving suspension to the circumferentialspeed of the drum. 6. Apparatus according to claim- 5, where the meansarranged on the shaft of the dr'urn inside the drum consist of adisplacement body: 7. Apparatus according'to claim 5, characterized bypump vanes arranged on the shaft ,of the 8. Apparatus for the continuouspurification of suspensions or sludges, especially of the fibrous pulpas used in the paper industry, which contain contaminations of higherspecific gravity, comprising a fixed casing, an enclosed drum havinginlet and discharge openings at its ends, respectively, and aperturesonly in its cylindrical face, rotatably arranged in said casing, saiddrum being provided with inwardly and outwardly extending radial annularmembers forming communicating annular compartments adjacent thecylindrical wall of said drum, said apertures being of a size exceedingthat of the contaminatio-ns, inlet means for admitting the suspensionand the contaminations into the interior of the drum, outletmeans forunobstructedly discharging the purified suspension from the interior ofthe drum at the end of the drum, means for the rapid rotation of thedrum to cause contaminations of higher Specific gravity to pass outthrough said apertures, deflecting surfaces arranged'inside'the drum,the interior of said drumbeing divided into a plurality of annularchambers, each adapted to deflect in a radial direction the flow whichis substantially axial.

the said deflecting surfaces consist ofj'transverse walls alternatinglyarranged on the shaft of the drum and on the wall of the drum.

12. Apparatus for the continuous purification of suspensions or sludges,especially of the fibrous pulps as used in the paper industry, whichcontain contaminations of higher specific gravity, comprising a fixedcasing, a drum rotatably ar-- ranged in the casing, said drum beingprovided with inwardly and outwardly extendin radial anthe drum at theend of the drum, means "for the rapid rotation of the drum to causecontaminations of higher specific gravity to pass out through saidapertures, and deflecting surfaces in the space between the outer wallof the drum and the fixed casing, the interior of said. drum beingdivided into a plurality of annular chambers, each adapted to deflect ina radial direction the flow which is'substantiallyaxial.

13. Apparatus according to claim 12, where the said deflecting surfacesconsist of transverse walls alternatingly arranged on the outer-side of,the drill]! and on the inner wall of the casing.

' 14.: Apparatus for the continuous purification 1 comprising a fixedcasing, a drum rotatably arnular members forming communicating annularcompartments adjacent thecylindrical wall of said drum, said wall of thedrum having aperture of a size exceeding that of the contaminations,inlet means for admitting the suspension and the contaminations into theinterior of the drum, outlet means for unobstructedly discharg-v rangedin said casing, said drum being provided with inwardly and outwardlyextending radial-annular members forming communicating annularcompartments adjacent the :cylindrical wall of said drum, said wallhaving apertures of a size exceeding that of the contaminations, inletmeans for admitting the suspension into the interior of the drum,means'for unobstructedly discharging the purified suspension from theinterior of the drum at the end of the drum, means for the rapidrotation of the drum to cause contamination of higher specific gravityto pass out through said apertures, deflecting surfaces in the spacebetween the outer wall of the drum and the, fixed casing, the interiorof said drum being divided into a plurality of annularchambers, eachadapted to deflect in a radial direction the flow which is substantiallyaxial, and outlet apertures in the wall of the casing disposed in frontof the deflecting surfaces.

15. Apparatus forthe. continuous purification of suspensions or sludges,especially of fibrous pulps as used in the paper industry, which containcontaminations of; higherspecific gravity,

comprising a fixed casing, a drum rotatably arranged insaid casing, saiddrum having a smaller diameter than the casing and apertures of a sizeexceeding that of the contamination, inlet means for admitting thesuspension into the interior of the drum, outlet means, forunobstructedly discharging the purified suspension from the interior ofthe drum at the endof the drum, means for the rapid rotation of s thedrum to cause con- -taminations of higher specific gravity to pass outthrough said apertures, deflecting surfaces in the space between theouter wall of the drum and the fixed casing, the interior of said drumbeing divided into a plurality-of annular chambers, each suspensions orsludges, especially of the fibrous pulps as used in the paper industry,which contain co'ntaminations of higher specific gravity, comprising afixed casing, a drum rotatably arranged in the casing, said drum beingprovided with inwardly and outwardly extending radial annular membersformingcommunicating annular compartments adjacent the cylindrical wallof ing the purified suspension from the interior'of (5 said drum; saidwall of the drum having aperturesof a size exceeding that'of thecontaminations, 'inl'et means for admitting the suspension and thecontaminations into the interior of the drum, outlet means forunobstructedly discharg,

ingthe purifiedsuspension from the interior of the drum at the end ofthe drum, means for the rapid rotation of the drum to causecontaminations of higher specific gravity to pass out through saidapertures, and means constituting part of 17. Apparatus for thecontinuous purification of suspensions or sludges,'especially of thefibrous pulps as used in the paper industry, which containcontaminations of higher specific gravity, consisting of a fixed casing,a drum rotatably arranged in said casing, said drum having a diametersmaller than that of the casing and apertures of a size exceeding thatof the contaminations, inlet means for admittin the suspension and thecontaminations into the interior of the. drum, outlet mean forunobstructedly discharging the purified suspension from the interior ofthe drum at the end of the drum, means for the rapid rotation of thedrum to cause contaminations of higher specific gravity to pass outthrough said apertures, and a tube co-axially arranged at the end of thedrum and adapted to remove contaminations of lower specific gravity,said tube having a smaller diameter than the outlet aperture of thedrum.

18. Apparatus for the continuous purification of suspensions or sludges,especially of the fibrous pulps as used in the paper industry, whichcontain contaminations of a higher specific gravity, comprising a fixedcasing, a drum rotatably arranged in said casing, said drum beingprovided with inwardly and outwardly extending radial annular membersforming communicating annular compartments adjacent the cylindrical wallof said drum, said wall having apertures of asize exceeding that of thecontaminations, inlet means for admitting the suspension and thecontaminations into the interior of the drum, outlet means forunobstructedly discharging the puriefied suspension from the interior ofthe drum at the end of the drum, and means for the rapid rotation of thedrum to cause contaminations of higher specific gravity to pass outthrough said apertures, said inlet means and outlet means havingapproximately radial ribs.

19. Apparatus for the continuous purification v of suspensions orsludges, especially of the fibrous pulps as used in the paper industry,which contain contaminations of a higher specific gravity, comprising afixed casing, a drum rotatably arranged in said casing, said drum beingprovided with inwardly and outwardly extending radial annular'membersforming communicating annula r compartments adjacent the cylindricalwall of said drum, said wall being provided with apertures, inlet meansfor admitting the suspension and the contaminations into the interior ofthe drum, outlet means for unobstructedly discharging the purifiedsuspension from the interior of the drum at the end of the drum, andmeans for the rapid rotation of the drum to cause contaminations ofhigher specific gravity to pas:- ut through said apertures, the ends ofthe drum hav ing inwardly projecting edges provided with ribs andgrooves.

r 20. Apparatus according to claim 8, where the wall of the drum isdivided after the deflecting surfaces, considered in the direction offlow, into a series of conical surfaces, openings being provided in thewall of the drum in front of the defleeting surfaces considered in thedirection of fiow.

HELMUTH BANNING.

